As a method of realizing low bit cost of a semiconductor memory device and enhancing memory performance thereof, a method of scaling down a size of a memory cell is widely accepted. However, scaling down the memory cell is getting technically difficult.
Hence it has been proposed to use organic molecules for a charge storage layer. The organic molecule can organically synthesize a variety of molecular structures and substituent groups. It can thus provide desired electrochemical properties. And constitutional unit of the organic molecule is small, thereby making it possible to realize scaling-down of the memory cell.
In a semiconductor memory device using organic molecules for a charge storage layer, further improvement in charge retention properties is required.